Yahoo Inc. (NASDAQ: YHOO) revealed a complete overhaul of Yahoo Mail last week to celebrate the email service’s 16th birthday, but the changes are not going over well with Yahoo users.

Thousands of Yahoo Mail users have complained to Yahoo about the Mail redesign on forums and on social media. Many are angry that key features of Yahoo Mail had been removed, while others have reported serious technical glitches.

So what are the actual complaints? Well, a major issue with the new Yahoo Mail is that users can no longer organize their inboxes by tabs or sort by sender, and new emails aren’t displayed in bold. Others have complained about being unable to view mail folders without leaving the inbox, and forums have been established to complain about the new location of the “delete” button. There’s isn’t even a button to print.

As far as actual technological errors, Yahoo Mail users have reported a broken autosave function, missing email contacts and even self-deleting emails. Many users on Twitter complain that the new Yahoo Mail is very slow.

These are just a few of the issues reported in the “bug or error” section of the Yahoo Mail feedback. At the time of writing, there are 6,811 complains.

The top complaint asks Yahoo to simply "Please Bring Back Tabs." It has received 35,482 votes and 2,890 comments at the time of writing, nearly all off them voicing complaints in varying degrees of anger. Yahoo has issued the following response:

Thank you for the feedback on the tab feature in Yahoo Mail. We deeply value how much our users care about Yahoo and are constantly engaging with our products.

The recent design changes in Yahoo Mail are important steps to building a more modern and personalized version. We recognize that this is a lot of change and are actively listening to user feedback so we can continuously make improvements.

Here is just a sampling of the complaints found on Twitter.

There are a lot of questions I want to ask the person in charge of the Yahoo! Mail redesign.